maskotherwise projection mask
(rus. маскаotherwise шаблон)
— a solid flat plate with an opaque image of the topological pattern and the areas transparent to the radiation outside of the pattern (positive process); in the negative process the topological pattern is transparent.

Description

The mask is one of the most important elements of the photolithographic process in microelectronics. Photolithography is carried out to apply a circuit pattern onto a wafer using a computer-controlled machine (stepper). Its aim is to create “windows” of a given configuration in the layer of photoresist to provide the etchant with access to the semiconductor wafer covered by an oxide film that is located under the photoresist layer. Such “windows” are formed by exposing the photoresist in a flux of ultraviolet laser radiation, as a result of which the photoresist becomes soluble (or insoluble). The configuration of such “windows” is determined by the mask; after applying the mask the resulting pattern is focused using a special lens system that reduces the pattern created by the mask to the required size of the circuit. A silicon wafer is held in place on a positioning table below the lens system, the table then moves the wafer so that all microprocessors on the wafer are successively treated. Ultraviolet laser rays pass through the open spaces of the mask. Under their influence the photosensitive layer in the corresponding area of the wafer becomes soluble and is then removed with organic solvents.